1. Field of Invention
The present invention relates to a method for forming a planarized dielectric layer. More particularly, the present invention relates to a method of forming a planarized dielectric layer such as a flowable oxide layer over a device substrate, and then treating the dielectric layer using a fluoride implant treatment so that the dielectric layer has a more stable dielectric constant and a lower leakage current, thereby improving its electrical properties.
2. Description of Related Art
In U.S. Pat. No. 4,756,977 by Haluska et al., a method of forming a silica dielectric layer over a device substrate is proposed. The method is to dissolve hydrogen silsesquioxane (HSQ) in a solvent to form a solution, and then the solution is spread over the electronic devices. Next, the solution is allowed to evaporate. Then, the substrate is heat-treated using a temperature of between 150.degree. C. to 1000.degree. C., thus forming a silica coating on top. The processing just ends there without mentioned anything about subsequent treatments.
In U.S. Pat. No. 5,441,765 by David S. et al., subsequent treatments of the dielectric layer formed by the aforementioned method are further described. In the patent, after the heat treatment of the substrate, the substrate is placed in a chamber exposed to a mixture containing gaseous hydrogen and an inert gas. For example, the inert gas is nitrogen, and the ratio of gaseous hydrogen to nitrogen, that is, H.sub.2 :N.sub.2 is about 10.about.15%:90.about.85%. Thereafter, the dielectric layer is annealed to lower its dielectric constant. However, nothing is mentioned about how to improve other electrical properties.
As the manufacturing of electronic devices is moving to the deep sub-micron regime, any dielectric film must have a narrow gap-filling capability in order to obtain a better planarization. Furthermore, the dielectric film must have good electrical properties such as a thermally stable dielectric constant and a low leakage current.
In light of the foregoing, there is a need in the art to provide an improved method of forming a planarized dielectric layer.